Bio Quiz 11/19

Describe TWO events that are common to both mitosis and meiosis that ensure the resulting daughter cells inherit the appropriate number of chromosomes.

1) Chromatin condenses 2) Alignment of chromosomes across center of cell prior to chromosome separation

The genetic composition of daughter cells produced by mitosis differs from that of the daughter cells produced by meiosis. Describe TWO features of the cell division processes that lead to these differences.

1) Mitosis = 1 division/2 cells result VS Meiosis = 2 divisions/4 cells result 2) Mitosis = no crossing over VS Meiosis = crossing over

During prophase I replicated homologous chromosomes pair up and undergo synapsis. What testable question is generated regarding synapsis and genetic variability by Figure 1 ? A. Is the distance between two gene loci related to crossover rate? B. Does crossing over occur more often in some chromosomes than in others? C. Is crossing over inhibited by methylation? D. Is crossing over promoted by methylation?

A. Is the distance between two gene loci related to crossover rate?

Scientists have found that DNA methylation suppresses crossing-over in the fungus Ascobolus immersus. Which of the following questions is most appropriately raised by this specific observation? A. Is the level of genetic variation in the gametes related to the amount of DNADNA methylation observed? B. Without crossing-over, will gametes be viable and be able to produce zygotes? C. Does DNADNA methylation result in shorter chromosomes? D. Is this species of fungus a diploid organism?

A. Is the level of genetic variation in the gametes related to the amount of DNADNA methylation observed?

Which of the following statements correctly describes the chromosomes in each daughter cell at the end of meiosis I? A. Each daughter cell contains 12 chromatids. Each chromatid is one of two from a single chromosome with the other one of the pair found in the other daughter cell. B. Each daughter cell contains 12 chromosomes, each composed of two chromatids. Since the chromosomes were randomly divided, one daughter cell may contain both of a pair of homologous chromosomes, while the other cell contains both of another pair of homologous chromosomes. C. Each daughter cell contains 12 chromosomes, each composed of two chromatids. Each chromosome is one of a pair of homologous chromosomes from the parent cell, with the other homologue found in the other daughter cell. D. Each daughter cell contains 24 separate chromatids. Since every two chromatids were originally joined, forming one homologous chromosome, the number of chromatids is divided by two to determine the number of chromosomes.

C. Each daughter cell contains 12 chromosomes, each composed of two chromatids. Each chromosome is one of a pair of homologous chromosomes from the parent cell, with the other homologue found in the other daughter cell.

Which of the following questions about genetic diversity could most appropriately be answered by analysis of the model in Figure 1 ? A. Does crossing-over generate more genetic diversity than the fusion of gametes does? B. Does DNADNA methylation prevent independent assortment during metaphase IIII? C. How does the independent assortment of the two sets of homologous chromosomes increase genetic diversity? D. Do daughter cells that are not genetically identical to parent cells produce viable zygotes?

C. How does the independent assortment of the two sets of homologous chromosomes increase genetic diversity?

Which of the following is the correct sequence of these events?

Condensation of chromosomes begins, synapsis occurs, crossing-over is completed, separation of homologous chromosomes begins

Explain how crossing over during meiosis increases genetic diversity.

Crossing over exchanges genetic material during meiosis, thus creating recombinant chromosomes and increasing diversity.

Both mitosis and meiosis begin with a parent cell that is diploid. Which of the following best describes how mitosis and meiosis result in daughter cells with different numbers of chromosomes? A. In mitosis, the chromosomes consist of a single chromatid, which is passed to two haploid daughter cells. In meiosis, the chromosomes consist of two chromatids during the first round of division and one chromatid during the second round of division, resulting in two haploid daughter cells. B. In mitosis, synapsis of homologous chromosomes results in four haploid daughter cells after one division. In meiosis, synapsis of homologous chromosomes occurs during the second division and results in four diploid daughter cells. C. Mitosis produces one identical daughter cell after one round of division. Meiosis has two rounds of division and doubles the number of chromosomes in the second round of division, producing four diploid cells. D. Mitosis produces two identical diploid daughter cells after one round of division. Meiosis produces four haploid daughter cells after two rounds of division.

D. Mitosis produces two identical diploid daughter cells after one round of division. Meiosis produces four haploid daughter cells after two rounds of division.

Saccharomyces cerevisiae is a diploid yeast species that can reproduce either sexually or asexually. An experiment was performed to induce mitotically dividing S. cerevisiae cells in G2 to undergo meiosis. Which of the following best describes the steps these cells will follow to form gametes? A. The first division will result in crossing over between homologous chromosomes, and the second division will reduce the original number of chromosomes by half in the daughter cells. B. The first division will reduce the number of chromosomes by half for each daughter cell, and the second division will result in each daughter cell having one-fourth of the original number of chromosomes. C. The first division will move single chromatids to each daughter cell, and the second division will double the number of chromosomes in each daughter cell. D. The first division will reduce the number of chromosomes by half for each daughter cell, and the second division will move single chromatids to each daughter cell.

D. The first division will reduce the number of chromosomes by half for each daughter cell, and the second division will move single chromatids to each daughter cell.

Explain how random assortment of chromosomes during meiosis increases genetic diversity.

Random alignment leads to new combinations of traits.

Describe the purpose of meiosis.

The purpose of meosis is to produce haploid gametes.